The present invention relates to a wear-resistant layer which is applied to a surface, which is to be protected, of a component which is subjected to mechanical and/or fluidic loads and substantially comprises amorphous or amorphous-nanocrystalline metals.
Components which are subjected to mechanical stresses from friction or around which media flow are generally subject to abrasive or erosive wear. In the field of internal-combustion engines, this wear occurs, for example in the case of piston engines, on valves, pistons or the like. In the field of gas turbines, furthermore, the components around which media flow need to be protected against erosion and corrosion.
The journal Metall, volume 36 (August 1982), pages 841 to 853, describes welding amorphous metal strips, due to their corrosion resistance and their high hardness and resistance to abrasion, to turbine blades of aircraft engines. Amorphous iron-base metals and the production of the metal strips using continuous quenching methods may be used for this purpose.
German Published Patent Application No. 38 00 454 describes a process for the production of corrosion-resistant and wear-resistant layers and shaped bodies made from metallic, amorphous materials, in which an amorphous powder which can be processed further by powder metallurgy is produced from metallic alloys, and this powder is then applied to the substrate, for example, by plasma spraying.
German Published Patent Application No. 38 14 444 describes amorphous alloys which are highly resistant to corrosion and substantially comprise at least one element selected from the group consisting of Ta and Nb and in addition may have at least one element selected from the group consisting of Ti and Zr, with Cu also always being a constituent. Numerous Cu-base alloys made from these elements are described, and these alloys are applied to a substrate by spray deposition.
German Published Patent Application No. 42 16 150 describes highly corrosion-resistant amorphous alloys based on Ti or Zr and Cr, which are described as having a high resistance to corrosion and wear and are applied to a substrate by sputtering or atomization.
German Published Patent Application No. 689 03 073 describes a thin, corrosion-resistant and heat-resistant film made from an aluminium alloy and a process for its production, in which the alloy contains, as further elements, Ni, Zr or Y and is applied by thin-film formation techniques, such as cathode sputtering, vacuum deposition or ion plating, to a substrate, such as, for example, a wire or a filament.
U.S. Pat. No. 5,389,226 describes electrodeposition of an amorphous microcrystalline (including nanocrystalline) Nixe2x80x94W alloy on a substrate, such as a part of an internal-combustion engine, the coating having a high hardness and being able to withstand wear and corrosion.
Japanese Published Patent Application No. 10096077 describes a gradient coating with a thickness of over 0.1 mm which is produced from an Al alloy, an element selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Ti, Zr and Y, rare earths and a misch metal by electron beam deposition on a substrate, the hardness of the coating being varied by the ratio between Al and the element from the group.
Chemical Abstracts XP002136889 describes the coating of a copper wire, which has a first, amorphous layer of an Nixe2x80x94P alloy, with an amorphous Pdxe2x80x94Cuxe2x80x94Si alloy by a laser, by which electrical contact elements are describes as becoming better able to withstand dissolution and abrasion.
It is an object of the present invention to provide a wear-resistant layer, which protects component surfaces that are acted on mechanically, for example, by friction, or fluidically against wear and increases the service life of these components. Suitable alloys are provided.
According to the present invention, the layer comprises an alloy based on Cuxe2x80x94Alxe2x80x94Ti(or xe2x80x94Ta or xe2x80x94Zr) or Ptxe2x80x94Alxe2x80x94Si or Taxe2x80x94Sixe2x80x94N, at least one rare earth and a transition metal, such as Cu or Ni or Co.
The advantage of wear-resistant layers of this type is that their alloys, unlike conventional crystalline metals, due to their amorphous or vitreous structure, do not have any grain boundaries and therefore have a high resistance to abrasive or erosive wear and have a high elastic restoring capacity.
In one example embodiment of the present invention, the layer substantially comprises an Nixe2x80x94W-base alloy, in which case the alloy may be Ni-rich and contain only between 20 and 40 atomic % of W. To achieve the amorphous or amorphous-nanocrystalline metal structure, the alloy may inexpensively be electrodeposited on the surface of the component to be coated. An alloy of this type which is present in the form of amorphous or amorphous-nanocrystalline metal has a high hardness, in particular due to the element W, and is extremely wear-resistant and temperature-resistant.
In an alternative example embodiment of the present invention, the wear-resistant layer may substantially comprise an alloy based on Cuxe2x80x94Alxe2x80x94Ti (or xe2x80x94Ta or xe2x80x94Zr) or Ptxe2x80x94Alxe2x80x94Si or Taxe2x80x94Sixe2x80x94N, in which case the layer may be applied to the surface of the component by PVD (physical vapor deposition) processes, and in particular Taxe2x80x94Sixe2x80x94N is suitable for applications at elevated temperatures.
The wear-resistant layer may substantially comprise an alloy based on Zrxe2x80x94Ti, in which case the amorphous or amorphous and nanocrystalline metal structure is produced by applying the alloy from the melt.
Alternatively, the wear-resistant layer may substantially comprise an alloy based on Fexe2x80x94Crxe2x80x94B, in which case the alloy is preferably iron-rich and contains approximately 70 atomic % of Fe. A wear-resistant layer of this type may be applied to the surface of the component by, for example, thermal spraying processes.
In a further example embodiment of the present invention, the wear-resistant layer may substantially comprise an alloy of Al, at least one rare earth and a transition metal, such as for example Cu or Ni or Co.
The layer may be applied to the root of a blade of a gas turbine to protect against fretting, since in that region, while the gas turbine is operating, a high level of frictional wear with high-frequency alternating loads with low amplitudes occurs.
In another example embodiment of the present invention, the wear-resistant layer may be applied to a component which substantially comprises fiber-reinforced plastic (FRP), in order to protect this component against erosion. In the case of FRP blades for compressors of gas turbines, examples of conventional arrangements for protecting against erosion are metallic foils, felts, wire meshes or coating materials, which have drawbacks in terms of the manufacturing costs or the required service life and are not yet usable.
In an alternative example embodiment of the present invention, the wear-resistant layer may be applied to a rotor carrier or rotor ring, which is configured as a disc or a ring, of an integrally bladed FRP rotor of a gas turbine, as protection against abrasive and/or erosive wear.
In an alternative use, the wear-resistant layer is applied to a component of a reciprocating engine, such as, for example, a valve, a camshaft, a crankshaft, a piston ring or a piston pin.